The present invention relates to a compressible fluid pressure actuator.
A pneumatic actuator using compressible fluid has been proposed and put to practical use as one of the actuators suited to a field of domestic robots and the like where safety is important. The Mckibben pneumatic actuator shown in FIG. 9 is proposed as one example of the pneumatic actuator. The Mckibben pneumatic actuator has a configuration in which a restricting means 303a configured by a fiber cord is arranged on the exterior surface of a tube-like elastic body 302a made of a rubber material, where both ends of the tube-like elastic body 302a are sealed in an air tight manner with the inner side sealing parts 321a, 322a and the fixed means 331a, 331b. When inner pressure is provided to the inner space 305a of the tube-like elastic body 302a with compressible fluid such as air through a tube-like fluid injecting/extracting member 311a and the inner side sealing part 321a formed with a conduit, the tube-like elastic body 302a attempts to expand mainly in the radial direction but is changed to a motion in the central axis direction of the tube-like elastic body 302a due to the effect of the restricting means 303a, whereby the entire length contracts. The Mckibben actuator is a safe and light actuator having flexibility as the Mckibben actuator is mainly configured by an elastic body (e.g., refer to Japanese Unexamined Patent Publication No. 59-197605).
Increasing the generative force or the displacement of the pneumatic actuator is achieved by enlarging the pneumatic actuator, but in such case, the amount of consumption of the compressible fluid increases since the volume of the inner space increases, and thus the response of the pneumatic actuator lowers as an issue. A similar pneumatic actuator is also disclosed in Japanese Examined Patent Publication No. 5-67397, but has a similar issue in that the response of the pneumatic actuator lowers due to change in the volume of the inner space. In order to resolve such issues, the volume occupied by the compressible fluid in the inner space must be reduced. A pneumatic actuator shown in FIG. 10 is proposed as one example of such pneumatic actuator. This pneumatic actuator is a double structure of the pneumatic actuator shown in FIG. 9, where the tube-like elastic body 302b including the restricting means 303b is fixed to the inner side sealing parts 321b, 321c formed with a conduit by means of the fixing means 331c, 331d inside the tube-like elastic body 302a. The inner space is thus divided into two inner spaces 305b, 305c. The fluid is supplied from the outside to the inner space 305c of the tube-like elastic body 302b through the tube-like fluid injecting/extracting member 311b, and the inner side sealing part 321c formed with conduit. The response of the pneumatic actuator is enhanced since the volume occupied by the compressible fluid with respect to the entire inner space is reduced when a non-compressible fluid is supplied to one of the two inner spaces, (refer to e.g., Japanese Examined Patent Publication No. 6-80321, Japanese Examined Patent Publication No. 5-48362).
Although the pneumatic actuator of FIG. 10 described above enhances response by reducing the volume occupied by the compressible fluid with respect to the entire inner space, the flexibility, which is a characteristic of the pneumatic actuator, is lost as an issue.
Therefore, an object of the present invention is to provide, in view of the above, a compressible fluid pressure actuator that enhances response while maintaining flexibility.